FAQ When do hermit crabs change shells?

Shell Changing Queue - Photo by Brian Hampson

FAQ When do hermit crabs change shells? Shell Changing Queue – Photo by Brian Hampson

Shell Changing Queue - Photo by Brian Hampson

Shell Changing Queue – Photo by Brian Hampson

Note: Fun shell changing videos at the bottom of the post.

crab_crazy asked:

Hi yall! About how often do hermies change there shells? I provide them with shells all the time! Two of my hermies just changed there shell! They look really cute, but, anyway. I was just wondering. Thanks yall!


Hi, Ronni,

Well, there is no exact answer to your question. Some crabs change shells all the time. My Fifi, a PP, after her first molt two months ago, has changed shells at least six times. She went hog-wild after I bought a lot of polished tapestry turbos on eBay.
Most of my crabs have either changed shells after a molt, or, in the case of new additions, immediately upon arrival because the shell they were in was damaged or painted.

Ecuadorians (c. compressus) are notorious for not wanting to switch shells. I had one switch right after I got him because his shell was too small, but of my other three, only one has switched. She has done so twice, again, only after molting. Of the other two, one has molted and has kept his original shell, and the other hasn’t molted yet. I sure wish he would, though, because the shell he’s in is possibly the ugliest shell I’ve ever seen.
Basically crabs will switch when they want to, and there is no hard and fast rule regarding when and how often. All you can do is keep a good supply of crab-friendly shells in your tank in appropriate sizes, and let them do the deed when they want to. Even if they don’t change into shells very often, they will spend a good deal of the time investigating every shell in the tank, whether it fits them or not. It’s one of their forms of entertainment, along with climbing, hiding and foraging. It’s best to keep at least three shells for every crab you have, one slightly smaller, one the same size, and one slightly bigger than the shell each crab is currently wearing, if at all possible. Also, having extras so you can rotate the stock occasionally will keep them more entertained and increase the chances of a switch.


I have a crab, Sabastion (Sab), who is too be for his shell, no matter how hard he trys to hide two or three of his walking legs are parially out, but he refuses to change shells. Any suggestions?


One of my crabbies look like he really needs to change shells but he hasn’t yet. The shell he’s in is looks like its getting too small for him and yet he refuses to change into another one. He’s been in there for a while. I’ve got tons of shells for him and the others to change into. Is this normal? I’ve got all shapes and sizes of shells (all non-painted of course) and different openings. Owning crabbies isn’t as easy as I expected.


There are times this does happen. The crabber thinks the shell isn’t a proper fit, yet the hermie just refuses to change shells regardless of the selections provided. The most one can do is offer a large variety of shells, and if the hermie finds that perfect shell many times they will move when they feel they need to. There are times too that the hermie seems to be a bit stubborn about change, especially if it is an E hermie. Sometimes it does help if one boils the shells to get the scent off of them to encourage the hermie to relook the shells over. By boiling it makes them think it is a new selection of shells. A few crabbers have had some luck by putting the hermie in need into iso with a wide selection of shells to choose from. This might make the hermie a little more secure about changing shells. No need to be concerned over their original shell being shell snatched while shopping.


Before boiling any shells I always let them sit in IO water for about 30 minutes. I’ve just heard too many stories about shells that look empty being , well, not empty. 30 minutes in the water will make even a stubborn crab emerge.
Here’s one of my stubbornest.

Hermit Crab in a Snail Shell

Hermit Crab in a Snail Shell

Hermit Crab in a Snail Shell

Hermit Crab in a Snail Shell

I know you can kind of see him beginning to peek out in the first one because he was getting curious but when he’s fully withdrawn, he’s invisible and because that shell is so light, it doesn’t seem overly heavy when you pick it up.


Fantastic point to bring up LolaGranola! *Clap* There haven’t been many, but have been occasions when hermies have been boiled due to not being able to see them within the shells. There was one that I remember reading that was sadly baked too due to the crabber not seeing the hermie within the hole of a choya log. Sad By the time she heard the clunk in the oven it was too late. Doing a complete ‘head/antenna count’ should be done before boiling or baking.


do they change shells only after a molt? do i need to buy the same shell he has. it looks to be his origanal one. its old looking.


Shell switching isn’t necessarily always tied to moulting. Some will change right away, some prefer to stay in their old shells. If the shell they are in fits and they are comfortable in it, they will stay put until they find one they like better. Some will change for no apparent reason and some will switch often (sometimes several times a day – going back and forth to/from old to new shells). If yours is having trouble fitting into it’s shell when it pulls itself in, you’ll want to supply it with a few more (at least 2-3 to choose from) in bigger sizes. Also, some species tend to be more into shell swapping.

A couple of things to look for…
*Different species have different body shapes so you’ll have to know which you have. If a Purple Pincher, stick with shells that have a more round shaped opening. If a Ruggie, go for more oval or “D” shaped openings.
*For size, it will depend upon how much too small the current shell is, but start with at least an 8th to a 4th of an inch wider than they are currently in when you measure across (side to side) the opening.
*Look for clean, smooth interiors and make sure there is no debris from the previous inhabitant stuck inside. Boil them and shake to listen for anything rattling inside and/or use a small baby bottle brush to clean around the curve inside.
*Look over the outside of the shell too – if there are any holes that will allow water to leak away from the Crab’s body inside the shell, discard the shell or use it somewhere else for decoration. A hole in the shell will allow the crab’s body to dry out or sand and grit to get in, harming your crab. A dry crab can’t breathe properly.
*Painted shells or natural is a personal choice, but most here recommend avoiding painted shells at all costs. Paint can chip off and is toxic to crabs if they eat it. There are tons of beautiful natural shells available that are better for the crab’s health.
*Where to find shells? We each have favorite places to look but Naples Seashell company has been a good choice for us. Their shells are measured for you and I haven’t gotten any yet that were damaged or unsuitable. They have a whole section on just Hermit Crab shells. Other sources if you are willing to go digging, are craft stores. Look for mixed baskets and discard the unsuitable ones – using the good ones. These baskets often come with many shells in them and the oyster or clam shells make nice little treat or feeding dishes. Other tiny shells in the basket can be glued onto containers for decoration.


Nearly all of my PPs, Strawberries, Indos and Ruggies greatly prefer turbos (round openings). The Ecuadorians really like the nerites, whale eyes and babylonia spirata (oval/D-shaped openings). I’ve posted this before, but there’s an eBay store, The Hermit Crab Shack, that has all natural shells at good prices, and Mike that runs it is very good about honoring requests about specific sizes, etc. Some of my crabbies have been in the same shell for nearly two years, and others switch on a regular basis. Happy shopping!


All our species of hermies Straw’s Rugs, Indo’s, and PP’s are in turbo shells too. Majority of our E’s are in turbo’s as well with only a couple who are in the shells with the D opening.

Sara Lewis and Randi Rotjan, New England Aquarium and Tufts University: Hermit Crab Vacancy Chains:

From BBC One: Hermit Crab Housing:

Photos of Coenobita Cavipes lining up for a shell change in Singapore